Viessmann VITODENS 100-W WB1B Series Installation And Service Instructions Manual page 78

Additional Information
Burner Program Sequence of Operation
Phase 0: Stand by
Complete shutdown until the next
call for heat. In this phase both the
combination gas valve and the blower
are not energized.
Phase 1: Stand-still status test
(blower)
A call for heat initiates internal blower
sensory communications to confirm
that the blower is truly in stand-still
position. Blower speed measured
must be < 300 rpm within a 70
second period.
Phase 2: Pre-purge speed test
Controller sends and receives signal
to / from fan speed controller to verify
maximum rpm of the blower.
Phase 3: Pre-purge
Pre-purge cycle starts within the pre-
programmed timing. Pre-purge timing
is in addition to previous phase (2).
The fan speed must be greater than
1500 rpm.
Phase 4: Pre-ignition
The ignition spark is initiated and
controlled.
Phase 5: Ignition / safety timing
The gas valve opens during the safety
timing period (4.8 secs.). If a flame is
detected, this phase ends immediately
in < 4.8 secs. If the flame is not
established after 3 trials, the burner
will lock out and will require a manual
reset.
Phase 6: Flame stabilization
Controller required time for flame
stabilization.
Phase 7: Forced low-fire
The controller will go into low-fire
until required modulation signal (high-
low) is processed (eg. boiler actual
water temperature).
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(continued)
Phase 8: Burner operation
At the end of the flame stabilization
period (5 sec.), a release for
modulation occurs and the burner
temperature controller will take over
from the flame safeguard. Forced
shutdown after 24 hours continuous
operation.
Phase 9: Post-purge speed test
Both gas valves are closed during this
phase. End call for heat.
Post-purge occurs during the
programmed period. If the fixed high
limit trips during normal operation, the
blower will purge for 15 minutes to
cool the heat exchanger.
Phase 10: Combination gas valve
proof of closure test
If during the normal operation of the
burner a controlled (or uncontrolled)
shut-down occurs, a complete
mechanical and electrical gas valve
proof of closure test will be performed
by the flame safeguard. After a
successful mechanical and electrical
proof of closure test, the flame
safeguard will expect that the flame
is not present. If, however, the flame
existed for a period of >30 seconds,
the flame safeguard will go into
permanent lock-out.